1. Field of the Invention
The present invention relates to acid compositions that are useful in food, medical, commercial and military industries and also as general household products. These compositions have a low pH, are relatively non-corrosive to metals, do not harm skin and are safe for use in food and beverages. The invention also relates to formulations that contain these acid compositions and to methods for using such formulations.
2. Description of the Background
Low pH compositions and solutions containing acidic compositions are used for various industrial and general household purposes, such as cleaning and sterilizing surfaces and articles of manufacture. Examples include well-known household cleansers and disinfectants, industrial microchip production and cleaning agents, and anti-microbials. To work both effectively and efficiently, these solutions typically contain strong acids or organic solvents, which present health concerns to the user, may be corrosive to the substances they are designed to clean (e.g. metals) and pose an ecological hazard with respect to disposal.
There have been a number of efforts aimed at developing less corrosive and less toxic acidic products. For example, U.S. Pat. No. 4,459,202 is directed to an acidic composition for recovering bituminous products from tar sands. Two strong and two weak acids are combined to form an acidic solvent that can be used to remove and recover the bituminous products. The composition is described as being non-corrosive and less hazardous to handle than other strongly acidic solutions.
The molecular effect of combining first and second strong acids with the third and fourth weaker acids forces the weaker acids to act as conjugate bases for the strong acids and to accept hydrogen ions (actually hydronium ions in aqueous solution) from the strong acids. The resulting acidic solution has a very low pH value, and a large amount of free hydrogen ions. However, the ability of this strong acidic composition to effectively function as a solvent may sometimes require more acid than would be considered safe or non-hazardous to human tissue. Moreover, there is no suggestion that this composition can be used in other applications, such as in products which come into contact with food. In fact, the composition cannot be used in connection with food and drink, as one or more of its components are not listed on the U.S. Food and Drug Administration list of substances considered generally recognized as safe (GRAS).
Various formulations using multiple acid compositions are disclosed in U.S. Pat. Nos. 4,675,120, 4,970,014, 4,970,015 and 5,019,288. Each of these compositions is described as either useful for well-acidizing, tertiary oil recovery, removing rust from metal, cleaning aluminum, radiator cleaning, boiler and heat exchanger cleaning, or copper cleaning. These compositions are described as generally non-corrosive to metal and relatively inert when contacted with human tissue. In addition, U.S. Pat. No. 4,483,887 describes a multiple acid solution useful for metal plating. U.S. Pat. No. 4,477,364 describes a multiple acid solution useful for cleaning glassware.
Although these acid-based solutions may be effective for the various described purposes, a major drawback is that certain formulations can cause skin irritation. For example, studies conducted using a topical skin disinfectant containing the core composition of U.S. Pat. No. 4,459,202 found that the product caused reddening of the skin and a burning sensation. Similar reddening of the skin and burning sensation resulted with a cleaning solution containing the core acid composition of U.S. Pat. No. 4,459,202. As such, these acid compositions cannot be safely used in products where skin contact is a possibility. In addition, such compositions cannot be used in products associated with foods or beverages. Further, many of these compositions require a multiplicity of components, leading to increased production costs.
U.S. Pat. No. 5,512,200 is directed to a multiple acid composition described as non-irritating to the skin and useful as a component of products such as cleansers, cosmetics and pharmaceutical agents. However, at least one of the components is not considered GRAS. Thus, despite the relatively inert nature of this composition, it cannot be used in foods or drinks, or in products associated with foods or drinks.
There is therefore a need for acid compositions comprising a minimum number of component acids, all of which components are approved by the Food and Drug Administration as GRAS, with broad utility for cleaning, sterilizing and anti-microbial uses that are effective, non-toxic and safe for use with food and food-related products.